1. Field of the Invention
The invention relates to a magnetofluidic suspension turbine of the type combining a radial fluidic bearing and a magnetic circuit adapted to generate a dynamic recentering return force on radial displacement of the rotor relative to the stator. The invention is more particularly concerned with an improvement to said magnetic circuit. A turbine of this kind can be used to drive a coating product sprayer member, which is generally in the form of a bowl, at a high rotation speed.
2. Description of the Prior Art
Document EP 0 567 436 describes a turbine of the above kind comprising a stator and a rotor and in which air injector means are provided to feed a laminar space defined between two respective facing plane surfaces (perpendicular to the required theoretical rotation axis of the rotor) of the rotor and of the stator and forming a radial fluidic bearing. This fluidic bearing is balanced by a magnetic circuit, part of which is in said rotor and part of which is in said stator and which comprises a defined radial airgap in substantially the same plane as the laminar space of the fluidic bearing. The magnetic circuit of the prior art device is remarkable in that it comprises magnets radially inside and magnets radially outside of the rotor and the stator, respectively, the magnets facing each other and being disposed symmetrically about the plane of the airgap.
Although a system of this kind is satisfactory in use, its industrial manufacture encounters a number of difficulties, in particular requiring difficult adjustments.
The difficulties encountered include the fact that the circumferencial field generated by an annular magnet is not homogeneous. Because of this, the magnetic axis of the rotor is rarely coincident with its geometrical axis. This can lead to an imbalance when the rotor is rotating at high speed; this defect is difficult to correct. Moreover, the magnets are glued into the rotor. It is therefore difficult to control the magnetic centering of the magnets and the size of the airgap, which causes disparities from one turbine to another.
For all these reasons it can be necessary to combine rotors and stators in matched pairs, which can subsequently lead to maintenance problems should it prove necessary to change the rotor. Finally, rare earth magnets have relatively low resistance to the centrifugal forces generated at high rotation speeds. The risk of a magnet of this kind bursting obliges the manufacturer to adopt a particular form of assembly (banding) around the magnets in the rotor. The invention eliminates all these disadvantages.